When taking a still image, a series of still images or video images using an imaging device, such as a camera, a camcorder, a video recorder, a mobile phone or the like, the user's hand may shake, causing the image formed on the image plane to shift laterally. The shift could blur the image. The shift can be caused by the tilting of the camera, or the lateral movement of the camera. FIG. 1 a shows the tilting of the camera due to the hand motion. As shown, the images of different parts of the scenery are formed on the same part of the image sensor. If the tilting angle is small, the shift is more or less equivalent to that caused by a lateral movement of the camera.
It is advantageous and desirable to stabilize the image in order to improve the viewing quality. Typical stabilization methods in the prior art can be divided into two types: one is based on software and one is based on a special optical device. The software method is applicable when the camera uses a solid-state imaging device such as CCD or CMOS for image formation. With the software method, the size of the CCD or CMOS imager must be larger than the size of the actual image for viewing or for recording so that the image can be effectively shifted using a real-time image processing technique to collectively move the pixel coordinates from one location to another. The software method is illustrated in FIGS. 2a and 2b, which show the same image is formed on a different part of the image sensor at different times due to hand motion.
With the other image stabilization method, it requires that at least one optical component of the imaging lens system be mechanically shifted in the x-y direction, as shown in FIG. 1b. The mechanical movement of the lens component involves complex and expensive mechanical structures.
In a mobile phone with limited image capability, the prior art method for image stabilization using software is impractical because a mobile phone in general is limited in its memory and image processing power. A mechanical structure is also undesirable because it is costly and requires space for implementation.
It is advantageous and desirable to provide a method and device for image stabilization without using a large image sensor or a movement mechanism to move the optical components in an imaging device.